#include<stdio.h>
#include<string.h>

int main(int argc, char *argv[])
{
	char str[] = "hello world";
	char c;

	char *p = str;
	int len = strlen(str);
	char *q = str + len - 1;

	while(p < q){
		c = *p;
		*p = *q;
		*q = c;
		p++;
		q--;
	}
	puts(str);
	return 0;
}


